Generally speaking, semiconductor devices such as integrated circuits (ICs) are manufactured by forming layered metallic circuit components and patterns on a semiconductor wafer. Numerous such ICs are formed on a single wafer. The individual ICs are separated from one another by a singulation process, such as sawing. Each IC is typically mounted on a metallic leadframe, and the IC-leadframe assembly is then encapsulated within a package. Package material, or “encapsulant” is commonly made from viscous or semi-viscous plastic or epoxy resin, which is cured to form a hardened protective cover to shield the protect the IC assembly from environmental hazards such as dust, heat, moisture, mechanical shock, and external electricity.
Integrated circuit packaging is usually accomplished using a molding process. The specifics of the process are influenced by many factors such as the IC and leadframe geometry, and encapsulant material used, but generally proceeds along the lines of one of the most widely used manufacturing processes, known as transfer molding. Molten encapsulant, sometimes also called mold compound, is compressed and is then distributed through a mold containing numerous IC-leadframe assemblies via a network of runners and gates. The IC assemblies include a number of ICs attached to suitable locations on an array of leadframes. Typically, multiple leadframes are manufactured in an array interconnected by sacrificial metal segments extending between the individual leadframes for manufacturing purposes.
Commonly, a mold for use in IC packaging is made up of a top half and a bottom half. The opposing halves enclose multiple cavities designed to receive an array of connected IC-leadframe assemblies, and to enclose them during molding and curing. Conventional molds include gates and runners which conduct the molten encapsulant to the series of mold cavities formed between the mated mold set halves. Gates are small openings into these cavities through which the encapsulant is introduced. Frequently, in what is commonly referred to as a side-gate system, encapsulant is injected into the mold cavities through gates formed in the molds that are lateral to the surface of the leadframe array. In conventional side-gate systems, the mold cavities are ordinarily filled in series, i.e., cavities that are nearer the encapsulant source get filled first, and the encapsulant flows through connecting gates to fill subsequent mold cavities.
When the encapsulant is sufficiently cured, the array of molded IC packages is removed from the mold, forcibly extracting the cured encapsulant from the mold. The individual packages are ultimately singulated from the array in which they were formed by cutting along the sacrificial segments pre-defined on the leadframe array. During the process of extracting the package array from the mold, package failures such as breaks, cracks, or chip-out may occur. In some instances, the gates of the mold may become blocked by cured encapsulant remaining in the gates after the IC package array is removed. This occurrence is more likely in instances where the sacrificial portion of the leadframe array spanning the mold gate, herein denominated the “strap” is insufficiently adhered to the cured encapsulant in the gate. In such cases where the bond between the encapsulant and the gate is stronger than that between the encapsulant and the strap, problems result. Upon extraction of the cured, molded package array from the mold, the connecting straps are pulled away from the encapsulant adhering to the mold gate. The resulting blockage of cured encapsulant remaining in the gate causes incomplete filling of the mold in subsequent attempts to inject encapsulant into the mold. This decreases productivity and necessitates increased downtime for mold cleaning or replacement.
Due to these and other technological challenges, improved IC package molding methods, improved package arrays, and improved leadframe arrays would be useful and advantageous in the arts. The present invention is directed to overcoming, or at least reducing the effects of one or more of the problems noted above.